JP4703581B2 - Conductive filler and solder paste - Google Patents
Conductive filler and solder paste Download PDFInfo
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- JP4703581B2 JP4703581B2 JP2007018633A JP2007018633A JP4703581B2 JP 4703581 B2 JP4703581 B2 JP 4703581B2 JP 2007018633 A JP2007018633 A JP 2007018633A JP 2007018633 A JP2007018633 A JP 2007018633A JP 4703581 B2 JP4703581 B2 JP 4703581B2
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Description
本発明は、電子機器の接合材料に用いられる導電性フィラーに関するものであり、特に鉛フリーはんだペースト、及び導電性接着剤に関する。 The present invention relates to a conductive filler used for a bonding material of an electronic device, and particularly relates to a lead-free solder paste and a conductive adhesive.
従来、電子機器等のはんだ実装では、Ｓｎ−３７Ｐｂ共晶はんだ（融点１８３℃）が、一般的に用いられてきたが、Ｐｂによる環境汚染、人体に対する有害性が問題視されるようになり、２００６年７月から欧州共同体（ＥＵ）ではＲｏＨＳ指令が施行されるなど、世界的にＰｂ規制強化の動きが高まり、Ｐｂを含まない代替はんだ材料及び接合技術の開発が進められている。
このような状況の中で、Ｓｎ−３７Ｐｂ共晶はんだに代わる接合材料、鉛フリーはんだとして、Ｓｎ−３．０Ａｇ−０．５Ｃｕ（融点２２０℃）はんだ（特許文献１参照）が広く知られているが、Ｓｎ−３７Ｐｂ共晶はんだに比べ融点が高く、実装温度、即ちリフロー熱処理温度、も上がるため、電子機器や基材への熱的負荷が大きくなり、耐熱性の低い材料では使用できないことから、低温で実装可能な低融点の鉛フリーはんだの開発が求められている。
尚、一般的に、リフロー熱処理温度は、はんだ合金融点＋１０〜５０℃の範囲で設定される。
Conventionally, Sn-37Pb eutectic solder (melting point: 183 ° C.) has been generally used in solder mounting of electronic devices and the like, but environmental pollution due to Pb, harmfulness to the human body has become a problem, In July 2006, the European Union (EU) enforced the RoHS directive, and global movements to strengthen Pb regulations have increased, and the development of alternative solder materials and joining technologies that do not contain Pb is being promoted.
Under such circumstances, Sn-3.0Ag-0.5Cu (melting point: 220 ° C.) solder (see Patent Document 1) is widely known as a joining material that replaces Sn-37Pb eutectic solder and lead-free solder. However, the melting point is higher than that of Sn-37Pb eutectic solder, and the mounting temperature, i.e., reflow heat treatment temperature, is increased, which increases the thermal load on electronic devices and base materials and cannot be used for materials with low heat resistance. Therefore, development of a low melting point lead-free solder that can be mounted at low temperature is required.
In general, the reflow heat treatment temperature is set in the range of the melting point of the solder alloy +10 to 50 ° C.
これに対し、低融点の鉛フリーはんだとしては、Ｓｎ、Ｉｎ、Ｂｉを主成分としたＳｎ−５２Ｉｎ（融点１１７℃）はんだ、Ｓｎ−５８Ｂｉ（融点１３９℃）はんだ（特許文献２、３参照）等がある。これらは、Ｓｎ−３７Ｐｂ共晶はんだよりも融点が低く、実装温度も１５０〜１８０℃の範囲の低温で使用できる利点があるが、Ｓｎ−５２Ｉｎはんだでは、Ｉｎが希少資源であり、また非常に高価な金属であるため、安定供給やコスト面での問題があり、Ｓｎ−５８Ｂｉはんだでは、材料自体が硬くて脆く、延性が低いなどの機械的性質に加え、熱疲労強度が低く、接続性に問題がある。
また、組立プロセスでは、複数回のはんだ実装が必要であり、前工程で実装した部分が再溶融して外れないように、徐々に融点の低いはんだを用いて実装温度を下げ、複数回のはんだ実装を行うが、上述した低融点の鉛フリーはんだでは、融点が低く、耐熱温度が低いので、最終段階のはんだ実装にしか使用できない、という問題があった。
なお、本発明者等は、以前、上記問題の解決手段の一つとして、Ｓｎ−３７Ｐｂ共晶はんだより低い実装温度で接続可能な鉛フリーの導電性材料で、且つ実装後は２６０℃でも接合強度を保持でき、複数回のはんだ実装にも対応可能な３種の金属粒子の混合体からなる導電性フィラーを提案した（特許文献４参照）。
On the other hand, as a low melting point lead-free solder, Sn-52In (melting point: 117 ° C.) solder mainly composed of Sn, In, Bi, Sn-58Bi (melting point: 139 ° C.) solder (see Patent Documents 2 and 3) Etc. These have the advantage that the melting point is lower than that of Sn-37Pb eutectic solder and the mounting temperature can be used at a low temperature in the range of 150 to 180 ° C. However, in Sn-52In solder, In is a scarce resource. Since it is an expensive metal, there are problems in terms of stable supply and cost. With Sn-58Bi solder, in addition to mechanical properties such as the material itself being hard and brittle and having low ductility, thermal fatigue strength is low, and connectivity There is a problem.
In addition, the assembly process requires multiple solder mountings, and the soldering temperature is gradually lowered using solder with a low melting point so that the parts mounted in the previous process are not remelted and removed. Although the above-described low melting point lead-free solder has a low melting point and a low heat-resistant temperature, there is a problem that it can be used only for solder mounting at the final stage.
In addition, the present inventors previously used a lead-free conductive material that can be connected at a mounting temperature lower than that of Sn-37Pb eutectic solder as one of the means for solving the above-mentioned problems. A conductive filler made of a mixture of three types of metal particles that can maintain strength and can be used for multiple solder mountings has been proposed (see Patent Document 4).
本発明は、上記の事情を鑑みてなされたものであり、Ｓｎ−３７Ｐｂ共晶はんだの実装温度（リフロー熱処理温度）条件よりも低温条件（ピーク温度１４９℃以上）で溶融接合でき、実装後は、耐熱２６０℃の接合材料として使用できる導電性フィラーを提供することを目的とする。また、前記導電性フィラーを用いたはんだペーストを提供することも本発明の目的である。 The present invention has been made in view of the above circumstances, and can be melt-bonded at a temperature lower than the mounting temperature (reflow heat treatment temperature) condition of Sn-37Pb eutectic solder (peak temperature of 149 ° C. or higher). Another object is to provide a conductive filler that can be used as a bonding material having a heat resistance of 260 ° C. It is also an object of the present invention to provide a solder paste using the conductive filler.
本発明者等は、上記課題を解決すべく鋭意検討した結果、本発明を成すに至った。
即ち、本発明の第一は、示差走査熱量測定（ＤＳＣ）で発熱ピークとして観測される準安定合金相を２５０〜２８５℃の範囲に少なくとも１つと、吸熱ピークとして観測される融点を５０〜９５℃の範囲と４００〜４７５℃の範囲の２箇所に少なくとも１つずつ有している金属粒子からなる導電性フィラーであって、上記金属粒子が、Ａｇ１０質量％、Ｂｉ２０質量％、Ｃｕ１５質量％、Ｉｎ２０質量％、及びＳｎ３５質量％の組成を有する合金からなる第１の金属粒子と、Ａｇ１０質量％、Ｂｉ５質量％、Ｃｕ６５質量％、Ｉｎ５質量％、及びＳｎ１５質量％の組成を有する合金からなる第２の金属粒子との混合体であり、その混合比が、該第１の金属粒子１００質量部に対し、該第２の金属粒子５３〜１４７質量部であることを特徴とする導電性フィラーである。
As a result of intensive studies to solve the above-mentioned problems, the present inventors have made the present invention.
That is, in the first aspect of the present invention, at least one metastable alloy phase observed as an exothermic peak in differential scanning calorimetry (DSC) is in the range of 250 to 285 ° C., and a melting point observed as an endothermic peak is 50 to 95. A conductive filler composed of metal particles having at least one each at two locations in the range of ° C and in the range of 400 to 475 ° C, wherein the metal particles are Ag 10 mass%, Bi 20 mass%, Cu 15 mass%, First metal particles made of an alloy having a composition of In 20% by mass and Sn 35% by mass, and an alloy having a composition of Ag 10% by mass, Bi 5% by mass, Cu 65% by mass, In 5% by mass and Sn 15% by mass . And a mixing ratio thereof is 53 to 147 parts by mass of the second metal particles with respect to 100 parts by mass of the first metal particles. It is a conductive filler.
また、本発明の第二は、示差走査熱量測定（ＤＳＣ）で発熱ピークとして観測される準安定合金相を２５０〜２８５℃の範囲に少なくとも１つと、吸熱ピークとして観測される融点を５０〜９５℃の範囲と４００〜４７５℃の範囲の２箇所に少なくとも１つずつ有している金属粒子からなる導電性フィラーであって、上記金属粒子が、Ａｇ１０質量％、Ｂｉ２０質量％、Ｃｕ１５質量％、Ｉｎ２０質量％、及びＳｎ３５質量％の組成を有する合金からなる第１の金属粒子と、Ａｇ１０質量％、Ｂｉ５質量％、Ｃｕ６５質量％、Ｉｎ５質量％、及びＳｎ１５質量％の組成を有する合金からなる第２の金属粒子と、Ａｇ３２質量％、Ｂｉ５質量％、Ｃｕ１０質量％、Ｉｎ５質量％、及びＳｎ４８質量％の組成を有する合金からなる第３の金属粒子との混合体であり、その混合比が、該第１の金属粒子１００質量部に対し、該第２の金属粒子５３〜１０５質量部、該第３の金属粒子２６〜１４４質量部であることを特徴とする導電性フィラーである。
本発明の第三は、本発明の第一、第二の導電性フィラーを含有することを特徴とするはんだペーストである。
In the second aspect of the present invention, at least one metastable alloy phase observed as an exothermic peak in differential scanning calorimetry (DSC) is in the range of 250 to 285 ° C., and a melting point observed as an endothermic peak is 50 to 95. A conductive filler composed of metal particles having at least one each at two locations in the range of ° C and in the range of 400 to 475 ° C, wherein the metal particles are Ag 10 mass%, Bi 20 mass%, Cu 15 mass%, First metal particles made of an alloy having a composition of In 20% by mass and Sn 35% by mass, and an alloy having a composition of Ag 10% by mass, Bi 5% by mass, Cu 65% by mass, In 5% by mass and Sn 15% by mass . and second metal particles, AG32 mass%, Bi 5 wt%, Cu10% by weight, In5 mass%, and a third metal particles made of an alloy having a composition of Sn48 wt% The mixing ratio is 53 to 105 parts by mass of the second metal particles and 26 to 144 parts by mass of the third metal particles with respect to 100 parts by mass of the first metal particles. It is an electroconductive filler characterized by these.
A third aspect of the present invention is a solder paste containing the first and second conductive fillers of the present invention.
本発明の導電性フィラーは、Ｓｎ−３７Ｐｂ共晶はんだの実装温度（リフロー熱処理温度）条件よりも低温条件（ピーク温度１４９℃以上）で溶融接合することが可能であり、実装後は、耐熱２６０℃の接合材料として使用することができるので、実装時の部品や基材、周辺機器への熱損傷を低減できると共に製造コスト、環境負荷を低減できる、という利点を有する。 The conductive filler of the present invention can be melt-bonded at a lower temperature condition (peak temperature of 149 ° C. or higher) than the mounting temperature (reflow heat treatment temperature) condition of Sn-37Pb eutectic solder. Since it can be used as a bonding material at 0 ° C., it has the advantage that thermal damage to components, base materials, and peripheral devices during mounting can be reduced, and manufacturing costs and environmental loads can be reduced.
本発明の導電性フィラーは、示差走査熱量測定（ＤＳＣ）で発熱ピークとして観測される準安定合金相を２５０〜２８５℃の範囲に少なくとも１つと、吸熱ピークとして観測される融点を５０〜９５℃の範囲と４００〜４７５℃の範囲の２箇所に少なくとも１つずつ有している金属粒子からなることを特徴とするものである。
尚、本発明における示差走査熱量測定（ＤＳＣ）での測定温度範囲は、３０〜６００℃とし、発熱量又は吸熱量が±１．５Ｊ／ｇ以上であるものを測定対象物由来のピークとして定量し、それ未満のピークは、分析精度の観点から除外するものとする。
また、本発明でいう「融点」とは、融解開始温度のことであり、示差走査熱量測定（ＤＳＣ）において固相線温度を指す。
The conductive filler of the present invention has at least one metastable alloy phase observed as an exothermic peak by differential scanning calorimetry (DSC) in the range of 250 to 285 ° C., and a melting point observed as an endothermic peak of 50 to 95 ° C. And a metal particle having at least one each in two places in the range of 400 to 475 ° C.
In addition, the measurement temperature range in the differential scanning calorimetry (DSC) in the present invention is 30 to 600 ° C., and a calorific value or an endothermic amount of ± 1.5 J / g or more is determined as a peak derived from the measurement object. However, peaks less than that are excluded from the viewpoint of analysis accuracy.
The “melting point” in the present invention is a melting start temperature, and indicates a solidus temperature in differential scanning calorimetry (DSC).
本発明の導電性フィラーとして好ましい金属粒子を例示すると、示差走査熱量測定（ＤＳＣ）で吸熱ピークとして観測される融点を５０〜９５℃の範囲に少なくとも１つ有する金属粒子（以下「第１の態様の金属粒子」ともいう。）と発熱ピークとして観測される準安定合金相を２４０〜２９０℃の範囲に少なくとも１つと、吸熱ピークで観測される融点を４８０〜５２０℃の範囲に少なくとも１つに有する金属粒子（以下「第２の態様の金属粒子」ともいう。）の混合体が挙げられる。
また、第１の態様の金属粒子と第２の態様の金属粒子、及び発熱ピークとして観測される準安定合金相を１１０〜１３０℃の範囲に少なくとも１つと、吸熱ピークで観測される融点を１６５〜２００℃の範囲と３２０〜３８０℃の範囲の２箇所に少なくとも１つずつに有する金属粒子（以下「第３の態様の金属粒子」ともいう。）の混合体が挙げられる。
Examples of metal particles that are preferable as the conductive filler of the present invention include metal particles having at least one melting point observed as an endothermic peak in differential scanning calorimetry (DSC) (hereinafter referred to as “first embodiment”). ) And at least one metastable alloy phase observed as an exothermic peak in the range of 240 to 290 ° C., and at least one melting point observed in the endothermic peak in the range of 480 to 520 ° C. And a mixture of metal particles (hereinafter also referred to as “metal particles of the second embodiment”).
In addition, at least one of the metal particles of the first embodiment, the metal particles of the second embodiment, and the metastable alloy phase observed as an exothermic peak is in the range of 110 to 130 ° C., and the melting point observed at the endothermic peak is 165. A mixture of metal particles (hereinafter also referred to as “metal particles of the third aspect”) having at least one each at two locations in a range of ˜200 ° C. and a range of 320 to 380 ° C. is mentioned.
熱処理により、金属粒子の最低融点以上の熱履歴が与えられると、金属粒子が溶融し、接合する。これにより、金属粒子間の熱拡散反応が加速的に進み、準安定合金相が減少して、最低融点よりも高温側に新たな安定合金相が形成される。即ち、ＤＳＣで発熱ピークとして観測される準安定合金相の存在が、該熱拡散反応を助長する効果がある。
第１の態様の金属粒子としては、Ａｇ５〜１５質量％、Ｂｉ１５〜２５質量％、Ｃｕ１０〜２０質量％、Ｉｎ１５〜２５質量％、及びＳｎ１５〜５５質量％の組成を有する合金からなる金属粒子（以下「第１の金属粒子」ともいう。）が例示される。より好ましくは、Ａｇ８〜１２質量％、Ｂｉ１７〜２３質量％、Ｃｕ１２〜１８質量％、Ｉｎ１７〜２３質量％、残部Ｓｎの組成を有する合金からなる金属粒子である。
If the heat treatment gives a thermal history equal to or higher than the minimum melting point of the metal particles, the metal particles are melted and joined. Thereby, the thermal diffusion reaction between the metal particles proceeds at an accelerated rate, the metastable alloy phase decreases, and a new stable alloy phase is formed on the higher temperature side than the lowest melting point. That is, the presence of a metastable alloy phase observed as an exothermic peak by DSC has an effect of promoting the thermal diffusion reaction.
As the metal particles of the first aspect, metal particles made of an alloy having a composition of Ag 5 to 15% by mass, Bi 15 to 25% by mass, Cu 10 to 20% by mass, In 15 to 25% by mass, and Sn 15 to 55% by mass ( Hereinafter, it is also referred to as “first metal particle”). More preferably, it is a metal particle which consists of an alloy which has composition of Ag8-12 mass%, Bi17-23 mass%, Cu12-18 mass%, In17-23 mass%, and remainder Sn.
第２の態様の金属粒子としては、Ａｇ５〜１５質量％、Ｂｉ２〜８質量％、Ｃｕ４９〜８１質量％、Ｉｎ２〜８質量％、及びＳｎ１０〜２０質量％の組成を有する合金からなる金属粒子（以下「第２の金属粒子」ともいう。）が例示される。より好ましくは、Ａｇ８〜１２質量％、Ｂｉ３〜７質量％、Ｉｎ３〜７質量％、Ｓｎ１２〜１８質量％、残部Ｃｕの組成を有する合金からなる金属粒子である。
また、第３の態様の金属粒子としては、Ａｇ２５〜４０質量％、Ｂｉ２〜８質量％、Ｃｕ５〜１５質量％、Ｉｎ２〜８質量％、及びＳｎ２９〜６６質量％の組成を有する合金からなる金属粒子（以下「第３の金属粒子」ともいう。）が例示される。より好ましくは、Ａｇ３０〜３５質量％、Ｂｉ３〜７質量％、Ｃｕ８〜１２質量％、Ｉｎ３〜７質量％、残部Ｓｎの組成を有する合金からなる金属粒子である。
As the metal particles of the second aspect, metal particles made of an alloy having a composition of Ag 5 to 15% by mass, Bi 2 to 8% by mass, Cu 49 to 81% by mass, In 2 to 8% by mass, and Sn 10 to 20% by mass ( Hereinafter, it is also referred to as “second metal particle”). More preferably, it is a metal particle which consists of an alloy which has composition of Ag8-12 mass%, Bi3-7 mass%, In3-7 mass%, Sn12-18 mass%, and remainder Cu.
Moreover, as a metal particle of 3rd aspect, it consists of an alloy which has composition of Ag25-40 mass%, Bi2-8 mass%, Cu5-15 mass%, In2-8 mass%, and Sn29-66 mass%. Particles (hereinafter also referred to as “third metal particles”) are exemplified. More preferably, it is a metal particle which consists of an alloy which has composition of Ag30-35 mass%, Bi3-7 mass%, Cu8-12 mass%, In3-7 mass%, and remainder Sn.
第１の態様の金属粒子と第２の態様の金属粒子との混合体における第１の態様の金属粒子と第２の態様の金属粒子の混合比は、第１の態様の金属粒子１００質量部に対して、第２の態様の金属粒子５０〜１５０質量部が好ましく、更には、第１の態様の金属粒子１００質量部に対して、第２の態様の金属粒子８０〜１２０質量部がより好ましい。
また、第１の態様の金属粒子と第２の態様の金属粒子と第３の態様の金属粒子との混合体における第１の態様の金属粒子と第２の態様の金属粒子と第３の態様の金属粒子の混合比は、第１の態様の金属粒子１００質量部に対して、第２の態様の金属粒子５０〜１５０質量部、第３の態様の金属粒子１〜１５０質量部が好ましく、更には、第１の態様の金属粒子１００質量部に対して、第２の態様の金属粒子８０〜１２０質量部、第３の態様の金属粒子８０〜１２０質量部がより好ましい。
The mixing ratio of the metal particles of the first embodiment and the metal particles of the second embodiment in the mixture of the metal particles of the first embodiment and the metal particles of the second embodiment is 100 parts by mass of the metal particles of the first embodiment. On the other hand, 50 to 150 parts by mass of the metal particles of the second aspect are preferable, and further, 80 to 120 parts by mass of the metal particles of the second aspect are more than 100 parts by mass of the metal particles of the first aspect. preferable.
The metal particles of the first embodiment, the metal particles of the second embodiment, and the third embodiment of the mixture of the metal particles of the first embodiment, the metal particles of the second embodiment, and the metal particles of the third embodiment. The mixing ratio of the metal particles is preferably 50 to 150 parts by mass of the metal particles of the second aspect and 1 to 150 parts by mass of the metal particles of the third aspect with respect to 100 parts by mass of the metal particles of the first aspect. Furthermore, 80 to 120 parts by mass of the metal particles of the second aspect and 80 to 120 parts by mass of the metal particles of the third aspect are more preferable with respect to 100 parts by mass of the metal particles of the first aspect.
上記金属粒子の粒子サイズと形状は、用途に応じて定めることができる。例えば、はんだペースト用途では、印刷性を重視して、平均粒径で２〜４０μｍの比較的真球度の高い粒子を使うことが好ましい。また、導電性接着剤用途としては、ビア充填では、穴埋め性を重視して、比較的真球度の高い粒子を使うことが好ましく、部品等の表面実装では、接触面積を増加させるために、異形粒子を使うことが好ましい。
尚、通常、微細な金属粒子は表面酸化されていることが多い。従って、上述の用途における熱処理による溶融、熱拡散を促進するためには、酸化膜を除去する活性剤を配合すること、または、加圧すること、の少なくとも一方を行うことが好ましく、両方行うことが更に好ましい。また、リフロー熱処理雰囲気は、大気より窒素の方が、加熱時の酸化を抑制できるのでより好ましい。
The particle size and shape of the metal particles can be determined according to the application. For example, in solder paste applications, it is preferable to use particles having a relatively high sphericity with an average particle diameter of 2 to 40 μm in consideration of printability. In addition, as a conductive adhesive application, in filling vias, it is preferable to use particles with relatively high sphericity with emphasis on hole filling properties, and in surface mounting of components and the like, in order to increase the contact area, It is preferable to use irregularly shaped particles.
Usually, fine metal particles are often surface oxidized. Therefore, in order to promote melting and thermal diffusion by the heat treatment in the above-mentioned application, it is preferable to mix at least one of an activator for removing the oxide film or pressurize, and to perform both. Further preferred. Further, as the reflow heat treatment atmosphere, nitrogen is more preferable than air because oxidation during heating can be suppressed.
本発明の導電性フィラーである第２及び第３の態様の金属粒子の製造方法としては、該金属粒子内に準安定合金相や安定合金相を形成させるために、急冷凝固法である不活性ガスアトマイズ法を採用することが望ましい。不活性ガスアトマイズ法では、通常、窒素ガス、アルゴンガス、ヘリウムガス等の不活性ガスが使用されるが、本発明に関しては、比重の軽いヘリウムガスを用いることが好ましく、冷却速度は、５００〜５０００℃／秒の範囲であるのが好ましい。
本発明のはんだペーストは、本発明の導電性フィラー、並びにロジン、溶剤、活性剤、及びチクソ剤等の成分からなるフラックスで構成される。はんだペーストにおける該導電性フィラーの含有率としては、８５〜９５質量％が好ましい。フラックスは、金属粒子からなる導電性フィラーの表面処理に最適で、熱処理時の該金属粒子の酸化膜を除去し、粒子の溶融、及び熱拡散による合金化を促進する。フラックスとしては、公知の材料を使用することができるが、更に有機アミンを酸化膜除去剤として加えるとより効果的であるので好ましい。また、必要に応じて、公知のフラックスに溶剤を加えて粘度を調整して使用しても良い。
As the method for producing the metal particles of the second and third aspects which are the conductive fillers of the present invention, in order to form a metastable alloy phase or a stable alloy phase in the metal particles, the inert solidification method is a rapid solidification method. It is desirable to adopt a gas atomizing method. In the inert gas atomization method, an inert gas such as nitrogen gas, argon gas, or helium gas is usually used. However, in the present invention, it is preferable to use helium gas having a low specific gravity, and the cooling rate is 500 to 5000. It is preferably in the range of ° C / second.
The solder paste of the present invention is composed of the conductive filler of the present invention and a flux composed of components such as rosin, a solvent, an activator, and a thixotropic agent. The content of the conductive filler in the solder paste is preferably 85 to 95% by mass. The flux is optimal for the surface treatment of the conductive filler made of metal particles, removes the oxide film of the metal particles during heat treatment, and promotes melting of the particles and alloying by thermal diffusion. A known material can be used as the flux, but it is preferable to add an organic amine as an oxide film remover because it is more effective. If necessary, a solvent may be added to a known flux to adjust the viscosity.
更に接合性を強化するためのバインダーとして、熱硬化性樹脂を含有させても良い。熱硬化性樹脂の種類には特に制限はなく、公知のものが使用可能である。例えば、レゾール型フェノ−ル樹脂、ノボラック型フェノール樹脂、ビスフェノール型エポキシ樹脂、ノボラック型エポキシ樹脂、１分子中の１個以上のグリシジル基を有する液状エポキシ化合物、メラミン樹脂、ユリア樹脂、キシレン樹脂、アルキッド樹脂、不飽和ポリエステル樹脂、アクリル樹脂、ポリイミド樹脂、フラン樹脂、ウレタン樹脂、ビスマレイミド−トリアジン樹脂、シリコーン樹脂などが挙げられる。尚、これらの樹脂中では、エポキシ樹脂が最も好ましい。また、熱硬化性樹脂は、モノマーの形態で含有させていても良い。バインダーには、硬化剤が含まれていても良く、アミン系エポキシ硬化剤、酸無水物系エポキシ硬化剤、イソシアネート系硬化剤、イミダゾール系硬化剤等が挙げられる。これら熱硬化性樹脂、硬化剤は、何れも１種単独で使用しても２種以上を併用しても良い。更にバインダーには、必要に応じて熱可塑性樹脂を含有させても良い。 Further, a thermosetting resin may be included as a binder for enhancing the bonding property. There is no restriction | limiting in particular in the kind of thermosetting resin, A well-known thing can be used. For example, resol type phenol resin, novolac type phenol resin, bisphenol type epoxy resin, novolac type epoxy resin, liquid epoxy compound having one or more glycidyl groups in one molecule, melamine resin, urea resin, xylene resin, alkyd Examples thereof include resins, unsaturated polyester resins, acrylic resins, polyimide resins, furan resins, urethane resins, bismaleimide-triazine resins, and silicone resins. Of these resins, epoxy resins are most preferred. Further, the thermosetting resin may be contained in the form of a monomer. The binder may contain a curing agent, and examples thereof include an amine epoxy curing agent, an acid anhydride epoxy curing agent, an isocyanate curing agent, and an imidazole curing agent. These thermosetting resins and curing agents may be used alone or in combination of two or more. Furthermore, you may make a binder contain a thermoplastic resin as needed.
以下、本発明を実施例などに基づいて更に具体的に説明するが、本発明はこれら実施例などにより何ら限定されるものではない。
尚、示差走査熱量測定は、島津製作所（株）製「ＤＳＣ−５０」を用い、窒素雰囲気下、昇温速度１０℃／分の条件で、３０〜６００℃の範囲において行った。
［実施例１］
（１）第１の金属粒子の製造
Ａｇ粒子１．０ｋｇ（純度９９質量％以上）、Ｂｉ粒子２．０ｋｇ（純度９９質量％以上）、Ｃｕ粒子１．５ｋｇ（純度９９質量％以上）、Ｉｎ粒子２．０ｋｇ（純度９９質量％以上）、Ｓｎ粒子３．５ｋｇ（純度９９質量％以上）、を黒鉛坩堝に入れ、９９体積％以上のヘリウム雰囲気下で、高周波誘導加熱装置により１４００℃まで加熱し、融解した。次に、この溶融金属を坩堝の先端より、ヘリウムガス雰囲気の噴霧槽内に導入した後、坩堝先端付近に設けられたガスノズルから、ヘリウムガス（純度９９体積％以上、酸素濃度０．１体積％未満、圧力２．５ＭＰａ）を噴出してアトマイズを行い、第１の金属粒子を作製した。この時の冷却速度は２６００℃／秒とした。
得られた第１の金属粒子を走査型電子顕微鏡（日立製作所（株）製：Ｓ−２７００）で観察したところ球状であった。この金属粒子を気流式分級機（日清エンジニアリング（株）製：ＴＣ−１５Ｎ）を用いて、５μｍの設定で分級した後に、そのオーバーカット粉を１５μｍの設定で、もう一度分級して得られたアンダーカット粉を回収した。この回収された第１の金属粒子の体積平均粒径は５．５μｍであった。
このようにして得られた第１の金属粒子を試料とし、示差走査熱量測定を行った。その結果、６６℃、８７℃、３８０℃の吸熱ピークが存在し、複数の融点を有することが確認された。
EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example etc., this invention is not limited at all by these Examples.
The differential scanning calorimetry was performed in a range of 30 to 600 ° C. using a “DSC-50” manufactured by Shimadzu Corporation under a nitrogen atmosphere under a temperature rising rate of 10 ° C./min.
[Example 1]
(1) Production of first metal particles 1.0 kg of Ag particles (purity 99% by mass or more), 2.0 kg of Bi particles (purity 99% by mass or more), 1.5 kg of Cu particles (purity 99% by mass or more), In 2.0 kg of particles (purity 99% by mass or more) and 3.5 kg of Sn particles (purity 99% by mass or more) are placed in a graphite crucible and heated to 1400 ° C. with a high-frequency induction heating apparatus in a helium atmosphere of 99% by volume or more. And melted. Next, after this molten metal is introduced from the tip of the crucible into a spray tank in a helium gas atmosphere, helium gas (purity 99 vol% or more, oxygen concentration 0.1 vol%) is supplied from a gas nozzle provided near the crucible tip. Less than the pressure of 2.5 MPa), atomization was performed to produce first metal particles. The cooling rate at this time was 2600 ° C./second.
When the obtained 1st metal particle was observed with the scanning electron microscope (Hitachi, Ltd. product: S-2700), it was spherical. The metal particles were classified using an airflow classifier (Nisshin Engineering Co., Ltd .: TC-15N) at a setting of 5 μm, and then the overcut powder was classified again at a setting of 15 μm. Undercut powder was collected. The collected first metal particles had a volume average particle size of 5.5 μm.
Differential scanning calorimetry was performed using the first metal particles thus obtained as a sample. As a result, it was confirmed that endothermic peaks of 66 ° C., 87 ° C., and 380 ° C. exist and have a plurality of melting points.
（２）第２の金属粒子の製造
Ａｇ粒子１．０ｋｇ（純度９９質量％以上）、Ｂｉ粒子０．５ｋｇ（純度９９質量％以上）、Ｃｕ粒子６．５ｋｇ（純度９９質量％以上）、Ｉｎ粒子０．５ｋｇ（純度９９質量％以上）、Ｓｎ粒子１．５ｋｇ（純度９９質量％以上）、を黒鉛坩堝に入れ、９９体積％以上のヘリウム雰囲気下で、高周波誘導加熱装置により１４００℃まで加熱し、融解した。次に、この溶融金属を坩堝の先端より、ヘリウムガス雰囲気の噴霧槽内に導入した後、坩堝先端付近に設けられたガスノズルから、ヘリウムガス（純度９９体積％以上、酸素濃度０．１体積％未満、圧力２．５ＭＰａ）を噴出してアトマイズを行い、第２の金属粒子を作製した。この時の冷却速度は２６００℃／秒とした。
得られた第２の金属粒子を走査型電子顕微鏡（日立製作所（株）製：Ｓ−２７００）で観察したところ球状であった。この金属粒子を気流式分級機（日清エンジニアリング（株）製：ＴＣ−１５Ｎ）を用いて、１．６μｍの設定で分級した後に、そのオーバーカット粉を１０μｍの設定で、もう一度分級して得られたアンダーカット粉を回収した。この回収された第２の金属粒子の体積平均粒径は２．９μｍであった。
このようにして得られた第２の金属粒子を試料とし、示差走査熱量測定を行った。その結果、４９６℃の吸熱ピークが存在し、融点を有することが確認された。また、２５４℃に発熱ピークが存在し、準安定合金相を有することが確認できた。
(2) Production of second metal particles Ag particles 1.0 kg (purity 99% by mass or more), Bi particles 0.5 kg (purity 99% by mass or more), Cu particles 6.5 kg (purity 99% by mass or more), In 0.5 kg of particles (purity 99% by mass or more) and 1.5 kg of Sn particles (purity 99% by mass or more) are placed in a graphite crucible and heated to 1400 ° C. with a high-frequency induction heating apparatus in a helium atmosphere of 99% by volume or more. And melted. Next, after this molten metal is introduced from the tip of the crucible into a spray tank in a helium gas atmosphere, helium gas (purity 99 vol% or more, oxygen concentration 0.1 vol%) is supplied from a gas nozzle provided near the crucible tip. And pressure was reduced to 2.5 MPa), atomization was performed, and second metal particles were produced. The cooling rate at this time was 2600 ° C./second.
When the obtained 2nd metal particle was observed with the scanning electron microscope (Hitachi Ltd. make: S-2700), it was spherical. After classifying the metal particles with an airflow classifier (Nisshin Engineering Co., Ltd .: TC-15N) at a setting of 1.6 μm, the overcut powder is classified again at a setting of 10 μm. The resulting undercut powder was recovered. The volume average particle size of the recovered second metal particles was 2.9 μm.
Differential scanning calorimetry was performed using the second metal particles thus obtained as a sample. As a result, it was confirmed that an endothermic peak at 496 ° C. was present and had a melting point. Moreover, the exothermic peak existed at 254 degreeC and it has confirmed having a metastable alloy phase.
（３）第３の金属粒子の製造
Ａｇ粒子３．２ｋｇ（純度９９質量％以上）、Ｂｉ粒子０．５ｋｇ（純度９９質量％以上）、Ｃｕ粒子１．０ｋｇ（純度９９質量％以上）、Ｉｎ粒子０．５ｋｇ（純度９９質量％以上）、Ｓｎ粒子４．８ｋｇ（純度９９質量％以上）、を黒鉛坩堝に入れ、９９体積％以上のヘリウム雰囲気下で、高周波誘導加熱装置により１４００℃まで加熱し、融解した。次に、この溶融金属を坩堝の先端より、ヘリウムガス雰囲気の噴霧槽内に導入した後、坩堝先端付近に設けられたガスノズルから、ヘリウムガス（純度９９体積％以上、酸素濃度０．１体積％未満、圧力２．５ＭＰａ）を噴出してアトマイズを行い、第３の金属粒子を作製した。この時の冷却速度は２６００℃／秒とした。
得られた第３の金属粒子を走査型電子顕微鏡（日立製作所（株）製：Ｓ−２７００）で観察したところ球状であった。この金属粒子を気流式分級機（日清エンジニアリング（株）製：ＴＣ−１５Ｎ）を用いて、５μｍの設定で分級した後に、そのオーバーカット粉を１５μｍの設定で、もう一度分級して得られたアンダーカット粉を回収した。この回収された第３の金属粒子の体積平均粒径は４．９μｍであった。
このようにして得られた第３の金属粒子を試料とし、示差走査熱量測定を行った。その結果、１９６℃、３５９℃、４１５℃の吸熱ピークが存在し、複数の融点を有することが確認された。また、１２０℃に発熱ピークが存在し、準安定合金相を有することが確認できた。
(3) Production of third metal particles 3.2 kg of Ag particles (purity 99% by mass or more), 0.5 kg of Bi particles (purity 99% by mass or more), 1.0 kg of Cu particles (purity 99% by mass or more), In 0.5 kg of particles (purity 99% by mass or more) and 4.8 kg of Sn particles (purity 99% by mass or more) are placed in a graphite crucible and heated to 1400 ° C. with a high-frequency induction heating apparatus in a helium atmosphere of 99% by volume or more. And melted. Next, after this molten metal is introduced from the tip of the crucible into a spray tank in a helium gas atmosphere, helium gas (purity 99 vol% or more, oxygen concentration 0.1 vol%) is supplied from a gas nozzle provided near the crucible tip. Less than the pressure of 2.5 MPa) and atomization was performed to produce third metal particles. The cooling rate at this time was 2600 ° C./second.
The obtained third metal particles were spherical when observed with a scanning electron microscope (manufactured by Hitachi, Ltd .: S-2700). The metal particles were classified using an airflow classifier (Nisshin Engineering Co., Ltd .: TC-15N) at a setting of 5 μm, and then the overcut powder was classified again at a setting of 15 μm. Undercut powder was collected. The volume average particle size of the recovered third metal particles was 4.9 μm.
Differential scanning calorimetry was performed using the third metal particles thus obtained as a sample. As a result, it was confirmed that endothermic peaks of 196 ° C., 359 ° C., and 415 ° C. exist and have a plurality of melting points. Moreover, the exothermic peak existed at 120 degreeC and it has confirmed having a metastable alloy phase.
（４）金属粒子混合体の製造
上記第１の金属粒子、第２の金属粒子、第３の金属粒子を重量比１００：１０５：１０３で混合して製造した導電性フィラーを試料とし、示差走査熱量測定を行った。この測定により得られたＤＳＣチャートを図１に示す。この図１が示すように、６６℃、８６℃、１９４℃、３３０℃、４３３℃に吸熱ピークが存在し、複数の融点を有することが確認された。また、２６２℃、２８３℃に発熱ピークが存在し、準安定合金相を有することが確認できた。
(4) Manufacture of metal particle mixture Differential scanning is performed using a conductive filler prepared by mixing the first metal particles, the second metal particles, and the third metal particles at a weight ratio of 100: 105: 103. Calorimetry was performed. The DSC chart obtained by this measurement is shown in FIG. As shown in FIG. 1, endothermic peaks exist at 66 ° C., 86 ° C., 194 ° C., 330 ° C., and 433 ° C., and it was confirmed that they have a plurality of melting points. Moreover, the exothermic peak exists in 262 degreeC and 283 degreeC, and it has confirmed having a metastable alloy phase.
（５）はんだペーストの製造
上記導電性フィラー９０．０質量％、ロジン系フラックス１０．０質量％を混合し、ソルダーソフナー（（株）マルコム製：ＳＰＳ−１）、脱泡混練機（松尾産業（株）製：ＳＮＢ−３５０）に順次かけてはんだペーストを作製した。
（６）融点、接合強度の確認
上記はんだペーストをアルミナ基板に載せ、大気雰囲気にて、ピーク温度１４９℃でリフロー熱処理した。熱処理装置は、ニホンハンダ（株）製のメッシュベルト式遠赤外線リフロー装置「ＲＱ−ＴＣ２３５」を使用した。温度プロファイルは、全工程が５分１５秒で、熱処理開始から１分で６９℃に達し、その後は徐々に昇温、３分で１１４℃、４分でピーク温度１４９℃に到達後、徐々に温度が降下、熱処理終了時は、１０８℃になる条件を採用した（以下「ピーク１４９℃熱処理」ともいう）。
(5) Manufacture of solder paste 90.0% by mass of the above conductive filler and 10.0% by mass of rosin-based flux are mixed, solder softener (manufactured by Malcolm Co., Ltd .: SPS-1), defoaming kneader (Matsuo Sangyo) Solder paste was produced by sequentially applying to SNB-350.
(6) Confirmation of melting point and bonding strength The solder paste was placed on an alumina substrate and subjected to reflow heat treatment at a peak temperature of 149 ° C. in an air atmosphere. As the heat treatment apparatus, a mesh belt type far-infrared reflow apparatus “RQ-TC235” manufactured by Nihon Solder Co., Ltd. was used. The temperature profile is 5 minutes and 15 seconds for all the steps, reaching 69 ° C. in 1 minute from the start of the heat treatment, and then gradually increasing the temperature, reaching 114 ° C. in 3 minutes, reaching the peak temperature of 149 ° C. in 4 minutes, and gradually When the temperature dropped and the heat treatment was completed, a condition of 108 ° C. was adopted (hereinafter also referred to as “peak 149 ° C. heat treatment”).
次に、この熱処理後のはんだペーストを試料とし、示差走査熱量測定を行った。この測定により得られたＤＳＣチャートを図２に示す。この図２に示すように、１０５℃、３２３℃、３５６℃、４３４℃に吸熱ピークが存在し、複数の融点を有することが確認された。２６０℃を境として吸熱量の量比を熱処理前と比較すると２６０℃以下の吸熱量が減少し、２６０℃以上の吸熱量が増加したのが判る。これは、低融点合金相が、熱処理により、拡散して高温側にシフトしたことを示すものである。また、２４４℃に発熱ピークが存在し、準安定合金相を有することが確認できた。熱量的には、熱処理前に比べ、約２２％減少しているのが判る。 Next, differential scanning calorimetry was performed using the solder paste after the heat treatment as a sample. The DSC chart obtained by this measurement is shown in FIG. As shown in FIG. 2, it was confirmed that there are endothermic peaks at 105 ° C., 323 ° C., 356 ° C., and 434 ° C., and a plurality of melting points. It can be seen that the endothermic amount at 260 ° C. or lower is decreased and the endothermic amount at 260 ° C. or higher is increased when the amount ratio of the endothermic amount is compared with that before the heat treatment at 260 ° C. This indicates that the low melting point alloy phase diffused and shifted to the high temperature side by the heat treatment. Moreover, the exothermic peak existed at 244 degreeC, and it has confirmed having a metastable alloy phase. It can be seen that the calorific value is reduced by about 22% compared to before the heat treatment.
次に、上記はんだペーストをＣｕ基板上に２ｍｍ×３．５ｍｍで印刷し、チップを搭載した後、大気雰囲気にて、前記の熱処理方法で、ピーク１４９℃熱処理してサンプルを作製した。印刷パターン形成は、マイクロテック（株）製の印刷機「ＭＴ−３２０ＴＶ」を用い、マスクは、メタルマスクで、スキージは、ウレタン製のものを用いた。マスクの開孔は、２ｍｍ×３．５ｍｍであり、厚みは、１００μｍである。印刷条件は、印刷速度１０ｍｍ／秒、印圧０．１ＭＰａ、スキージ圧０．２ＭＰａ、背圧０．１ＭＰａ、アタック角度２０°、クリアランス０ｍｍ、印刷回数１回とした。また、チップは、２ｍｍ×２ｍｍで、厚みが０．５ｍｍのＣｕチップを用いた。
次に、常温（２５℃）で、前記作製サンプルの剪断方向のチップ接合強度をプッシュ・プルゲージにより、押し速度１０ｍｍ／ｍｉｎで測定し、単位面積で換算したところ７．１ＭＰａであった。更に前記作製サンプルをホットプレート上で２６０℃まで加熱し、２６０℃で１分間保持した状態で、前記と同じ方法で剪断方向のチップ接合強度を測定したところ、３．２ＭＰａであり、２６０℃でも接合強度を保持できる耐熱性を確認することができた。
Next, the solder paste was printed on a Cu substrate with a size of 2 mm × 3.5 mm, and after mounting the chip, a sample was prepared by heat treatment at a peak of 149 ° C. in the air atmosphere by the heat treatment method described above. For the printing pattern formation, a printing machine “MT-320TV” manufactured by Microtech Co., Ltd. was used, the mask was a metal mask, and the squeegee was made of urethane. The opening of the mask is 2 mm × 3.5 mm, and the thickness is 100 μm. The printing conditions were a printing speed of 10 mm / second, a printing pressure of 0.1 MPa, a squeegee pressure of 0.2 MPa, a back pressure of 0.1 MPa, an attack angle of 20 °, a clearance of 0 mm, and a printing frequency of once. The chip used was a 2 mm × 2 mm Cu chip having a thickness of 0.5 mm.
Next, at normal temperature (25 ° C.), the chip bonding strength in the shear direction of the prepared sample was measured with a push-pull gauge at a pushing speed of 10 mm / min, and converted to unit area, which was 7.1 MPa. Furthermore, when the fabricated sample was heated to 260 ° C. on a hot plate and held at 260 ° C. for 1 minute, the chip bond strength in the shear direction was measured by the same method as described above, and it was 3.2 MPa. The heat resistance capable of maintaining the bonding strength could be confirmed.
［実施例２〜７］
実施例１記載の第１の金属粒子、第２の金属粒子、第３の金属粒子の混合比を変えた混合体を導電性フィラーとして、実施例１と同じ方法によりペースト化、熱処理した後、チップ接合強度を測定したものを、表１に実施例２〜７として示す。
［比較例１〜９］
また、表１には、比較例として、第２の金属粒子が下限未満の場合（比較例１）、第２の金属粒子が含まれない場合（比較例２）、第２の金属粒子が下限未満の場合（比較例３）、第１の金属粒子が単独の場合（比較例４）、第３の金属粒子が含まれず、第２の金属粒子が上限を越える場合（比較例５）、第３の金属粒子が含まれず、第２の金属粒子が下限未満の場合（比較例６）、第３の金属粒子が上限を越える場合（比較例７）、並びに従来のはんだ材料を測定した結果を示す。比較例８は、Ｓｎ−３７Ｐｂ共晶はんだ、比較例９は、Ｓｎ−５８Ｂｉ共晶はんだの例である。
[Examples 2 to 7]
After making the mixture which changed the mixing ratio of the 1st metal particle of Example 1, the 2nd metal particle, and the 3rd metal particle into a conductive filler, and pasting by the same method as Example 1, and heat-treating, Table 1 shows the results of measuring the chip bonding strength as Examples 2 to 7.
[Comparative Examples 1 to 9]
In Table 1, as a comparative example, when the second metal particle is less than the lower limit (Comparative Example 1), when the second metal particle is not included (Comparative Example 2), the second metal particle is the lower limit. Less than (Comparative Example 3), when the first metal particles are alone (Comparative Example 4), when the third metal particles are not included, and when the second metal particles exceed the upper limit (Comparative Example 5), 3 is not included, the second metal particle is less than the lower limit (Comparative Example 6), the third metal particle exceeds the upper limit (Comparative Example 7), and the results of measuring the conventional solder material Show. Comparative Example 8 is an example of Sn-37Pb eutectic solder, and Comparative Example 9 is an example of Sn-58Bi eutectic solder.
表１の結果から明らかなように、２６０℃に加熱した状態において、比較例８、９の共晶はんだが再溶融するのに対し、実施例１〜７では、２ＭＰａ以上の接合強度があり、接合状態を保持できる耐熱性があることが判る。また、実施例１では、Ｉｎ比が９．９質量％まで低減されている。
以上、説明したように本発明の導電性フィラーを用いることで、Ｓｎ−３７Ｐｂ共晶はんだの実装温度（リフロー熱処理温度）条件よりも低温条件、即ちピーク温度１４９℃以上、で溶融接合でき、実装時の部品や基材、周辺機器への熱損傷を低減できると共に、実装後は、耐熱２６０℃の接合材料として使用できるので、耐熱信頼性が高く、また、一種のペーストで複数回のはんだ実装に対応できるので、製造コストも低減できる接合材料を提供することができる。
As is clear from the results in Table 1, in the state heated to 260 ° C., the eutectic solders of Comparative Examples 8 and 9 remelt, whereas in Examples 1 to 7, there is a bonding strength of 2 MPa or more. It can be seen that there is heat resistance that can maintain the bonded state. Moreover, in Example 1, In ratio is reduced to 9.9 mass%.
As described above, by using the conductive filler of the present invention, it can be melt-bonded at a temperature lower than the mounting temperature (reflow heat treatment temperature) condition of Sn-37Pb eutectic solder, that is, at a peak temperature of 149 ° C. or higher. Thermal damage to parts, base materials, and peripheral equipment can be reduced, and after mounting, it can be used as a heat-resistant 260 ° C bonding material, so heat resistance is high, and solder mounting multiple times with a kind of paste Therefore, it is possible to provide a bonding material that can reduce the manufacturing cost.
本発明の導電性フィラーは、Ｓｎ−３７Ｐｂ共晶はんだの実装温度（リフロー熱処理）条件よりも低温条件（ピーク温度１４９℃以上）で溶融接合でき、且つ、実装後は、高耐熱の接合材料としての活用が期待できる。 The conductive filler of the present invention can be melt-bonded at a lower temperature (peak temperature of 149 ° C. or higher) than the mounting temperature (reflow heat treatment) condition of Sn-37Pb eutectic solder, and after mounting, as a highly heat-resistant bonding material Can be expected.
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